Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001aas...199.0201r&link_type=abstract
American Astronomical Society, 199th AAS Meeting, #02.01; Bulletin of the American Astronomical Society, Vol. 33, p.1303
Astronomy and Astrophysics
Astronomy
Scientific paper
Although discoveries at the edge of the universe fascinate us all, there are still exciting things to be learned from the nearby universe. From the study of nearby galaxies, we learn details that are invaluable for interpreting observations of distant galaxies, where such details are unobservable. I will discuss recent and future studies for several unique nearby galaxies. For our Galaxy and M31, new data and simulations reveal important facts about their nuclei, their stellar streams, their halos, their masses, and their future interaction. Conclusions from these studies overturn some generally held beliefs. At slightly greater distance, the complex kinematics of the prototypical polar ring galaxy NGC 4650A demand explanation. Polar rings are generally believed to have formed in a `second event' in which the central lenticular galaxy acquired gas. Recently, Tremaine and Yu (2000) have suggested a novel model in which polar orbits arise kinematically. A resonance between the pattern speed of an intitally retrograde halo (slowing to zero or even prograde rotation due to infalling material) and the rates of precession of the angular mementum vectors of disk stars, may ultimately levitate some stellar orbits. The model predicts that the ring contains two equal, counterrotating star streams. Predictions are rare in galaxy studies, and there are telescopes and spectrographs which can now test this prediction. The model would also explain the counterrotating streams of disk stars in NGC 4550. Finally I will discuss NGC 6872 and IC 4970, a large tidally disturbed spiral with a small companion. Recent observations reveal details not known at the time of the modeling by Mihos, Bothun, and Richstone (1993).
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